This invention relates to fetal probes, and more particularly to a connector assembly for coupling a fetal electrode to a remote monitoring device.
One type of fetal probe comprises a bipolar fetal electrode commonly used to monitor fetal heart rate during birth. This type of probe consists of a spiral fetal electrode mounted on a carrier along with an electrically isolated maternal electrode. A twisted pair of wires are connected at one end to the fetal and maternal electrodes and at their opposite ends to a connector. One such connector consists of a pair of axially spaced electrodes which are electrically isolated and each of which is connected to one of the wires. The connector is adapted to be coupled to a socket having axially spaced connectors which, in turn, are coupled by a cable to the monitor.
Initially, the twisted pair of conductors and the connector are disposed in a hollow drive tube. The end of the drive tube is inserted into the mother""s cervix until the forward end contacts the fetus. The role of the drive tube is to push forwardly until the spiral fetal electrode at the forward end makes contact with the fetal epidermis. The drive tube is then rotated to screw the spiral electrode into the fetal epidermis. The drive tube is then slid over the wires and the connector while the bipolar electrodes and the twisted pair of wires remain within the mother and connected to the fetus. The removal of prior art tubes required the dexterous manipulation of the drive tube which were designed to maintain a grip on the twisted pair so as to insure that the drive tube is engaged at the distal end. Defeating the grip tended to be cumbersome.
In these prior art connectors, the connector at the other end of the twisted pair of conductors is exposed. Such exposed electrodes could soil or contact energy sources and tend to be disconcerting to the patient or her partner.
In one type of assembly the socket for receiving the connector is mounted on a support or circuit board which electrically connects to a plate mounted on the mother""s leg by an adhesive pad and provides a reference for the fetal and maternal electrodes. The support or circuit board connects to the leg plate by a snap electrical connector. Such snap connectors do not uniformly provide a distinct snap to indicate that good electrical contact has been achieved. In addition, the forces necessary to couple and disconnect the contacts are not consistent. As a result, medical personnel may not be aware should a good electrical connection not be achieved.
Federal Food and Drug Administration regulations now require that the connectors be designed such that no conductive connector that is remote from the patient can contact earth or any possibly hazardous voltages. One example of a connector designed for compliance with the modern regulations is disclosed in co-pending application Ser. No. 09/237,468, which is hereby incorporated herein by reference. This connector includes first and second tubular contacts axially separated and electrically isolated from each other. The tubular contacts are positioned to make electrical contact with complementary contact members in the coupling device. An elongated tubular insulating sheath covers the tubular contacts so that they are not exposed to potentially hazardous voltages.
The present invention provides another connector assembly embodiment for a fetal scalp electrode used to monitor fetal heart rate. The connector assembly is used in conjunction with a fetal monitor coupling device and includes a holder formed of an insulating material and a fetal electrode and a maternal electrode secured to the holder. Each wire of an insulated pair of elongated flexible wires is electrically connected to a respective one of the fetal and maternal electrodes. The connector assembly further includes a connector having a pin contact electrically connected to one of the wires and a cylindrical contact electrically connected to the other of the wires. The cylindrical contact is mounted coaxially with the pin contact so that the contacts are electrically isolated from each other and are positioned to make electrical contact with complementary contacts in the coupling device.
The connector assembly also preferably includes an elongated tubular sheath that covers the connector and is sized to be received in the coupling device. The sheath has a first end extending over and receiving the ends of the pair of flexible wires, and a second end that is open and spaced from each of the contacts so that a gap is formed between the contacts and the second end of the sheath.
The coupling device includes a housing defining a cavity having an opening for receiving the connector. A center conductor is mounted in the cavity and includes a tubular portion substantially coaxial with and spaced from the opening. Inside the tubular portion is an internal spring contact that includes an inwardly biased resilient spring contact finger extending away from the opening. An outer conductor is also mounted in the cavity and includes a tubular portion that is coaxial with and electrically isolated from the center conductor. The outer conductor also includes an outwardly biased resilient spring contact finger extending from the tubular portion and away from the opening.